Vertical Mill Application:
Vertical mills are energy-saving, versatile new powder grinding equipment, suitable for industries such as cement, power, chemicals, and non-metallic minerals. They are particularly suitable for grinding black clinker in cement plants and preparing raw materials for white cement factories. With high efficiency, low electricity consumption, large drying capacity, easily adjustable product fineness, uniform particle size, easy-to-control chemical composition, low noise, minimal metal wear, dust-free operation, simple system process flow, small land occupation, and cost-effectiveness, they are widely used in the cement and non-metallic mineral industries both domestically and internationally.
Main Structure and Functions:
The RHM and PRM vertical mills are mainly composed of separators, grinding rollers, grinding disks, pressure devices, reducers, electric motors, and casings, etc.
The separator is a crucial component determining the fineness of the product, consisting of a variable-speed transmission device, wheels, air guide vanes, housing, coarse powder discharge cone, and exhaust outlet, similar in working principle to the classifier.
The grinding roller is the main component for material crushing and grinding, with two pairs of grinding rollers installed inside. Each pair is mounted on the same shaft and rotates at different speeds.
The millstone is fixed on the output shaft of the reducer, with the upper part serving as a material bed, featuring annular grooves.
The pressure unit is a component that provides grinding pressure, consisting of a high-pressure oil station, hydraulic cylinder rod, accumulator, etc., capable of applying sufficient pressure to the roller to crush the material.
The reducer, besides transmitting power, also bears the weight and grinding force of the millstone.
Working Principle:
The motor drives the mill disc through a reduction gear, while hot air enters the mill from the intake. Materials fall onto the center of the disc through the feeding port and, due to centrifugal force, move towards the disc's edge. As they pass through the annular grooves, they are crushed by the roller, then continue moving outward until they are picked up by the air ring's airflow. Larger particles fall back onto the disc for regrinding. When materials in the airflow pass through the separator, coarse materials fall onto the disc via a conical hopper, while fine powder exits with the air flow, collected in the system's dust collection unit as the final product. Materials are dried during contact with the gas to achieve the required moisture content. By adjusting the angle of the guide vanes and the speed of the separator's rotor, products of varying fineness can be obtained.
Features:
Compared to ball mills, vertical mills have the following features:
1. High powder grinding efficiency, vertical mills utilize the powder bed grinding principle for material grinding, featuring low energy consumption. The electrical consumption of the powder grinding system is 20-30% lower than that of the ball mill system, and the energy-saving effect becomes even more pronounced with the increase of raw material moisture.
2. High drying capacity; vertical mills use gas conveyance for material. When grinding materials with high moisture content, the air intake temperature can be controlled to achieve the desired moisture level. Inside the vertical mill, it can dry materials with up to 12-15% moisture content, whereas ball mills can only dry materials to around -4% moisture.
3. The product's chemical composition is stable with even particle grading. Since the material only stays in the vertical mill for 2-3 minutes, compared to 15-20 minutes in ball milling, the chemical composition of the product produced by the vertical mill can be quickly measured and corrected. The product's chemical composition fluctuates little, which is beneficial for homogenization. Additionally, qualified products in the vertical mill can be separated out in a timely manner, avoiding over-grinding. The fineness of the product can be rapidly changed by adjusting the speed of the separator rotor, ensuring uniform particle size, which is advantageous for calcination.
4. The process is simple, with a small building area and minimal space occupancy. The vertical mill features a separator, eliminating the need for a classifier and elevator. The dust-laden gas exiting the mill can be directly fed into a dust collector or baghouse, where it is collected as the finished product. Thus, the process is straightforward, the layout is compact, and the building area is only 50-60% of the ball mill system.
5. Low noise, minimal dust, and clean operating environment. The vertical mill operates without direct contact between the grinding roller and the grinding disc, eliminating the metallic impact sounds of steel balls colliding in a ball mill or striking the lining plates. Due to the reduced noise, it is approximately 20-25 decibels quieter than a ball mill. Additionally, the vertical mill employs full sealing and operates under a vacuum, resulting in less dust and a cleaner environment.
6. Low metal loss and high utilization rate; due to the absence of direct metal contact during the vertical mill's operation, wear is minimal. The unit product wear is typically 5-10 grams per ton, and the lifespan of roller sleeves and liners for grinding cement raw materials exceeds 8,000 hours, with an operational rate reaching 95%.
7. Economical in use.
